1. I-V conversion Using a current mirror and load as ground connected PMOS. Possibly the best way to get linear I-V conversion. We evaluated the use of NMOS/PMOS in diode configuration in all possible ways (Doesn’t work) – Always, non-linearity comes when transistor goes from cut-off to saturation. – So, we need to give a constant fixed biasing.
Simulation Result When all 12 bits are ON => Output voltage = 0.75V When all 12 bits are OFF => Output voltage= 2.5V Total Swing = 2.5V to 0.75V
Binary weighted section design Need unit current sources. From our calculation, we need a maximum total current of 3.84uA from binary weighted 4 LSB bits => unit current source = 256nA.
Binary weighted section design 4 bit LSB binary encoder
Binary encoder simulation result Matches perfectly with what was desired. Swing = 2.5V- 0.75V = 1.75V Voltage change when all 4 bits ON = Output voltage = 2.5V – 6.835mV = 2.4931V